Ice When he isn’t snowboarding or volunteering for Engineers Without Borders, Dave Williams spends his days thinking about something most of us take for granted: ice. As he discovered on a volunteer trip to Haiti in 2002, ice can be a godsend to a poor village, keeping fish fresh on a journey to market or preserving vaccines. But how do you make it without electricity, without access to coolants like Freon or fuels like propane? Williams, 26, knew that forcing compressed air through a hole in the middle of a pipe causes hot and cold air to flow from opposite ends, a phenomenon known as the Ranque-Hilsch… [via] Link.